The present invention relates to a wire bonding inspecting apparatus, and more specifically to an apparatus suitable for use to automatize the wire bonding inspection process.
After wire bonding between a semiconductor chip and leads have been completed, it is necessary to inspect whether wires are bonded at the correct positions, in straight lines without being curved, not disconnected, etc.
If these inspections are carried out by a worker's visual inspection with a microscope, there arise various problems in that the inspection criteria differ or defects are missed dependng on the inspecting worker; a long inspection time is required from the end of wire bonding to the start of inspection without being inspected immediately, etc., so that recently wire bonding has been inspected by means of automatized inspecting apparatuses.
In the ordinary automatized inspecting apparatus, an optical image of a semiconductor chip on which wires are bonded is focused onto an image sensor and converted into electrical image signals for inspection.
In the prior art inspecting apparatus; however, there exists a problem in that the apparatus is not applicable to various lengths of bonded wires. For instance, where a wire 2 bonded to an electrode 3 of a semiconductor chip 1 is short as shown in FIG. 4, the whole bonded wire 2 lies within an image area 101, so that the bonded wire 2 can be inspected with respect to the shape, etc., by using an image within a partially enlarged image area 101 as shown in FIG. 5.
However, where the bonded wire 2a is long as shown in FIG. 6, the whole long wire cannot be seen within one image area 102. To see the whole long wire within the image area 102, the magnification of the lens of the inspecting apparatus must be reduced, thus resulting in a higher cost because the magnification must be adjusted according to the size of an object to be inspected.
In addition, since there exists a limitation in the resolution of an image apparatus or an image processing apparatus, there exists the case where it is impossible to reduce the lens magnification when a necessary inspection precision must be satisfied. In summary, in the prior art inspecting apparatus, it has been impossible to inspect bonded wires of different lengths while satisfying the high inspection precision required.